Quinidine

Brand names

• Apo-Quin-G
• Apo-Quinidine
• Biquin Durules
• Cardioquin
• Cin-Quin
• Duraquin
• Natisedine
• Novo-Quinidin
• Quinaglute Dura-Tabs
• Quinate
• Quinatime
• Quinidex Extentabs
• Quinobarb [CD]
• Quinora
• Quin-Release
• SK-Quinidine Sulfate

Usage

To correct irregular heartbeats (cardiac arrhythmias).

How it works

Quinidine slows nerve impulses in the heart and reduces the sensitivity of heart tissue to certain nerve impulses, thus stabilizing heartbeat.

Side effects

Serious

Dizziness, lightheadedness, or fainting; any change in vision; fever; severe headache; ringing or buzzing in the ears; hearing loss; skin rash or hives; shortness of breath or wheezing; rapid heartbeat; unusual bleeding or bruising; unexplained fatigue.

Common

Diarrhea, loss of appetite, bitter taste, flushing and itching skin, nausea, vomiting, stomach pain or cramps.

Less common

Mental confusion, rash.

Possible interactions

Other medicaments:

Quinidine taken concurrently with:

• aspirin may prolong the bleeding time.
• beta blockers may result in additive and undesirable beta-blockade; lower starting doses may be needed for both medicines.
• cisapride (Propulsid) may lead to serious heart rhythm problems.
• codeine may blunt the effectiveness of codeine.
• dextromethorphan (the DM in many cough preparations) can lead to dextromethorphan toxicity.
• dofetilide (Tikosyn) may lead to serious heart rhythm problems. Prudent to wait 4.32 half lives after stopping a prior class-one antiarrhythmic or other QTc prolonging medicament before starting dofetilide.
• fluoxetine (Prozac) may lead to quinidine or fluoxetine toxicity.
• gatifloxacin (Tequin), grepafloxacin (Raxar) , moxifloxacin (Avelox) or sparfloxacin (Zagam) may lead to abnormal heartbeats.
• metformin (Glucophage) may increase risk of lactic acidosis.
• nisoldipine (Sular) may blunt nisoldipine benefits.
• tramadol (Ultram) may lead to tramadol toxicity.
• tricyclic antidepressants may result in antidepressant toxicity.
• venlafaxine (Effexor) may result in venlafaxine toxicity.

Quinidine may increase the effects of:



• anticoagulants (Coumadin, etc.) and increase the risk of bleeding; more frequent INR (prothrombin time or protime) testing is needed.
• digitoxin and digoxin (Lanoxin) and cause digitalis toxicity.
• disopyramide (Norpace).
• metformin (Glucophage).
• propafenone (Rythmol) may lead to propafenone toxicity. Careful patient follow up is critical as propafenone dosing adjustments may be required.
• tricyclic antidepressants (doxepin).
• warfarin (Coumadin) and may result in coagulation changes (inconsistent effect). More frequent INR checks are prudent.

The following medicaments may increase the effects of quinidine:



• amiodarone (Cordarone).
• cimetidine (Tagamet).
• delavirdine (Rescriptor).
• erythromycin (various).
• itraconazole (Sporanox).
• ketoconazole (Nizoral).
• quinupristin/dalfopristin (Synercid) may lead to serious heart rhythm problems-extremely careful quinidine level follow up and careful patient monitoring are critical if these medicines must be combined.
• ritonavir (Norvir) , nelfinavir (Viracept) and perhaps other protease inhibitors.
• sertraline (Zoloft).
• verapamil (Verelan).

The following medicaments may decrease the effects of quinidine:



• barbiturates (phenobarbital, etc.).
• phenytoin (Dilantin) or fosphenytoin (Cerebyx).
• rifabutin (Mycobutin).
• rifampin (Rifadin, Rimactane).
• sucralfate (Carafate).

Herbal medicines or minerals:

Kola, St, John's wort, ma huang and yohimbe may cause additive heart rate or rhythm problems. These are not advisable if you have heart rhythm difficulties. Using St. John's wort, ma huang, or kola while taking this medicine may result in unacceptable heart stimulation. Belladonna, henbane, scopolia, pheasant's eye extract or lily of the valley or squill powdered extracts should not be taken if you have abnormal heart rhythms. Since St. John's wort and quinidine may increase sun sensitivity, the combination is not advised.

Alcohol:

Alcohol may enhance the blood-pressure-lowering effects of this medicament.

Tobacco smoking:

Nicotine can increase irritability of the heart and aggravate rhythm disorders. Avoid all forms of tobacco.

Exposure to sun:

This medicament may cause photosensitivity.